The present invention relates, in general, to sensors, and more particularly, to a novel optical sensor.
Optical sensors previously have used glass fiber optic cables as sensors to detect pH and to detect the presence of chemicals such as carbon dioxide, carbon monoxide, and ammonia. The prior optical sensors generally expose a small section of a fiber optic cable, and apply a sol-gel derived silica glass containing a chemically sensitive dye to the outside of the exposed fiber cable. When exposed to different levels of a chemical analyte, the transmissive capability of the fiber optic cable is altered thereby changing the light that passes through the cable.
One problem with the prior sensors is the manufacturing cost. A portion of the cladding must be removed in a central portion of the cable, and then the sol-gel is applied to the exposed cable. Removing the cladding and applying the sol-gel is a labor-intensive and expensive operation. Furthermore, it is difficult to produce an array of multiple sensors suitable for sensing multiple chemicals and elements. Additionally, it is difficult to control the thickness and uniformity of the sol-gel coating, thus, it is difficult to control the response time of the sensor.
Accordingly, it is desirable to have an optical sensor that is easy to manufacture, that has a low manufacturing cost, that has a well controlled response time, and that can easily be formed into an array of multiple sensor elements.